tv.js: better handling of "taphold" menu on IE10

Previously I turned on the menu accidentally way too often, the previous
workaround wasn't really effective. In addition of checking if the window
scrolls, also I needed to check whether the popup menu was scrolling.

Also, change some function names to be clearer and more searchable.
tv.js: fix derp from previous commit 6f4ec9a2

I renamed the play function to playvideo and missed a spot where it was used.